1. Field of the Invention
The present invention relates generally to a seat reclining mechanism for vehicles and more particularly to a seat reclining mechanism having a reduction gear mechanism which includes an internal and an external gear supported on an eccentric shaft.
2. Description of the Prior Art
A conventional seat reclining mechanism for an automobile comprises a first bracket attached to a seat back, a second bracket for seat cushion, and a reduction gear mechanism disposed between the two brackets for changing the position of the first bracket i.e., reclining position of the seat back relative to the fixed position of the seat cushion. The reduction gear mechanism usually includes an internal gear on the seat back bracket and an external gear on the seat cushion bracket. The two gears are in engagement with each other by an eccentric shaft on which the gears are supported. A rotation of the eccentric shaft causes a displacement of the circumferential position of both gears thereby to produce a relative rotation of the internal gear with respect to the external. This will cause a change in the inclination angle of the two seat portion, i.e., seat back and seat cushion. In the seat reclining mechanism of the above type, the reduction gear mechanism requires a relatively large reduction gear ratios so that any reclining position of the seat back relative to the cushion may be kept mostly by the friction force between the eccentric shaft and the internal and external gears.